The structure & development of the mosses and ferns (Archegoniatae) . the inner cells of thelateral segments. The vascular cylinderof the root is usuallytetrarch. At four pointsnear the periphery smallspiral or annular tracheidsappear, and from them theformation of the largersecondary tracheids pro-ceeds toward the phloem is made upof nearly uniform cellswith moderately thickcolourlesswalls, A bundle-sheath is not clearly to bemade out (Fig. 137). The cotyledon is des-titute of the stipules foundin the perfect leaves of theMarattiacea:;, but they arewell developed in the thirdleaf,
The structure & development of the mosses and ferns (Archegoniatae) . the inner cells of thelateral segments. The vascular cylinderof the root is usuallytetrarch. At four pointsnear the periphery smallspiral or annular tracheidsappear, and from them theformation of the largersecondary tracheids pro-ceeds toward the phloem is made upof nearly uniform cellswith moderately thickcolourlesswalls, A bundle-sheath is not clearly to bemade out (Fig. 137). The cotyledon is des-titute of the stipules foundin the perfect leaves of theMarattiacea:;, but they arewell developed in the thirdleaf, where they form twoconspicuous appendagesclasping the base of the next VOUnc>eSt leaf The ^^-^39-—^^««^«-0<2^/«-s- (Baker), a, Longitudinal ?^ ^ _ section of the young sporophyte, showing the distri- edgeS of these stipules are bution of the vascular bundles, X6; /, leaves; s(, cjompwhal- ^prr3tp anH tViP stem apex ; r, a root;y; the foot; B, young sporo- somewnat serrate, ana tne p^yte with the prothaiuum (/r), stiii of the two much like two bivalve shells. The strictly dichotomouscharacter of the cotyledon is gradually replaced in the laterleaves by the pinnate arrangement, both of the divisions of theleaf and the venation. This is brought about in both cases byan unequal dichotomy, by which one branch develops more 268 MOSSES- AND FERNS CHAP. Strongly than the other, so that the latter appears the assumption of the pinnate form the leaf also developsthe wings or appendages upon the axis between the the fully-developed leaves of the mature sporophyte, the lasttrace of this is seen in the ultimate branching of the veins,which is always dichotomous. The second root arises close to the base of the second leaf,and at first there seems to be one root formed at the base ofeach of the young leaves ; in the older sporophyte the roots aremore numerous. Holle ^ states that this is not the case inMarattia, where only one root is
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
